A parallel printer interface has previously been used between an IBM PC and a printer. Information was transmitted only from the IBM PC to the printer since the printer was a unidirectional printer, that is, a printer capable of only receiving information. As a result, the unidirectional printer required a printer operator panel at the printer to enable an operator to ascertain why the printer could no longer receive data from the IBM PC, for example. Thus, this prior printer interface could not be efficiently utilized if the printer was remote from the operator such as when driving the printer via a Local Area Network (LAN) or when the printer was shared by a plurality of users.
The IBM PS/2 personal computer has a bi-directional parallel interface for using a software program, which is known as Data Migration Facility, in which data can be transferred from a 51/4" disk of the IBM PC to a 31/2" disk of the PS/2 personal computer to enable transfer of data from an IBM PC to a PS/2 personal computer. However, the PS/2 personal computer has not been capable of receiving information from a printer nor has there been a printer capable of supplying information to the PS/2 computer if the PS/2 computer were capable of receiving the information. Therefore, even with the PS/2 computer, it has been necessary for the operator to be near the printer to allow the operator to view the printer operator panel to determine the problem whenever information could not be sent to the printer.
While the PS/2 computer has not been capable of receiving information from a printer, U.S. Pat. No. 4,651,278 to Herzog et al has communication from a host system to an all points addressable printer and vice versa by a printer interface to that the printer is bi-directional. However, there does not appear to be communication from the printer to the host system after printing begins. Therefore, information is not sent from the printer to the host system to inform a remote user of why information cannot be sent to the printer, for example.
The interface of the aforesaid Herzog et al patent is an independent interface using a specific language. The interface of the aforesaid Herzog et al patent also transmits the information in structured field data streams, which are blocks, and not bytes. Thus, there can be no interruption of each block in the aforesaid Herzog et al patent to permit the printer to communicate with the host system.